1. Field of the Invention
The invention relates to a wellbore machining device and in particular a machining device for down-hole operation.
2. Background of the Invention
In drilling a wellbore or in oil production, there is a need for down-hole machining tubular components, for example of a production tubing or a casing down-hole the wellbore. To provide for a casing junction, a window has to be milled to the casing and a pipe branching off has to be trimmed and sealed to provide for a smooth transition. Another need is down-hole cutting of a casing or to provide support for a lock hanger. Another problem is cleaning and sealing leaking connections, for example of a production tubing and up to now down-hole welding of tubular components is a challenge.
From GB 2 129 350 A, a remotely controllable cutting apparatus is known to cut drainage slots into a liner down in a borehole. The apparatus comprises an elongated frame which can be clamped by hydraulic jacks to the liner. The frame is rotatably supported by the jacks and movably guides a cross table movably supporting a milling tool. The position of the milling tool is monitored through a television camera.
From GB 2 353 813 A, a wellbore machining device is known comprising a tool unit having a milling tool for cutting a hole into a casing at a position a junction is needed. The path on which the milling tool is moving while milling is controlled by a mechanical template defining the shape of the hole to be cut to the casing.
Known prior art down-hole machining devices are often subject to vibrations, which reduce efficiency and precision of the machining operation and in particular accelerate wear and increase machining time. For example, windows cut into a casing by prior art down-hole milling operation are often rough and cause damage to sophisticated equipment which thereafter has to be run through the window. Milling a window with such a device will be time consuming, in particular, since the milling operation often has to be interrupted and the tool has to be retracted to the surface level raising the time needed for tripping of the tool. Relocating the tool to the exact position is also time consuming.